In order to effectively utilize mobile network resources, the 3rd Generation Partnership Project (3GPP) provides the MBMS, which is the technology for transmitting data from a data source to multiple target mobile terminals. MBMS achieves resource sharing of networks (including core network and access network) and improves utilization rate of network resources, in particular air interface resources.
In a Long Term Evolution (LTE) system, a UE (or a terminal) is notified of possible changes of an MBMS, including session start, service carrier update or session stop etc., wherein Downlink Control Information (DCI) and an MBMS-Radio Network Temporary Identifier (M-RNTI) may be sent on a Physical Downlink Control Channel (PDCCH) at first. The UE further reads a Multicast Control Channel (MCCH) message according to related information in the DCI, which is called an MCCH notification mechanism. The MCCH will send specific service configuration parameters, such as service ID, Radio Link Control (RLC) of a service, Media Access Control (MAC), configuration parameters of a physical layer, and etc.
In the LTE system, MBMS has two carrying modes: broadcasting mode and enhanced broadcasting mode. Without multicast mode, a network side cannot know which MBMS the UE receives or intends to receive. The enhanced broadcast is between a broadcast and a multicast, and absorbs advantages of simple flow of the broadcast and optimized resources of the multicast. With the enhanced broadcasting carrying of the MBMS, a UE can log in to/log out of a Broadcast Multicast-Service Center (BM-SC) only by joining process/leaving process on an application layer without any signaling interaction or information storage on a carrying network layer. The enhanced broadcast is optimized and expanded from the broadcast, for example in an access network, the enhanced broadcast will not send data to a cell without a receiving user. For the enhanced MBMS, it is necessary to consider the state and number of the UE receiving the MBMS during configuring System Frame Number (SFN) and allocating resources, so the UE which receives or intends to receive the MBMS needs to feed information back, which is called the uplink feedback of the MBMS. In order to enable/disable Multimedia Broadcast Single Frequency Network (MBSFN) transmission in 3GPP Rel10 MBMS, the network side needs to acquire receiving state information of the UE, such as the number of UEs which are receiving given MBMS, therefore, a mechanism is needed to trigger a UE to report its receiving state information.
In order that the network side can acquire the number of users requiring MBMS in each cell, the MBMS system introduces a counting process.
The counting process refers to that: at start of an MBMS session or during the session (also called recounting), the network side counts the number of users receiving or intending to receive an MBMS in a cell to determine whether to adopt the MBSFN transmission. Intending to receive the MBMS refers to: the UE prepares to receive an MBMS from the MBSFN, and the UE monitors a notification message of the MCCH. When preparing to initiate a counting/recounting process, the network side adds the identifier and access probability of the MBMS into access information of the MCCH. The reason for using the access probability is that not all users are needed to be connected for feedback and as long as the feedback number reaches a threshold; otherwise, many idle users may cause uplink congestion.